Sensory receptors on the tarsi and palps of ticks detect and discriminate between the various chemical and physical stimuli that are behaviorally important to the tick. Extracellular recordings from single afferent neurons in Amblyomma americanum and Rhipicephalus sanguineus are being used to determine the physiological characteristics of these peripheral receptor systems. The goals of this research include the identification and characterization of the receptors specifically sensitive to the following: temperature; humidity; sex and/or aggregation pheromones; host-related airborne stimuli; repellent; and substances--such as amino acids, sugar, salts and water--that are present on the surface of a host. Fundamental knowledge of the sensory-behavior mechanisms in ticks can be applied to the eventual regulation of these vectors of human and animal disease.